Gender and vesico-ureteral reflux: a multivariate analysis

The aim of this retrospective cohort study was to describe the characteristics of patients with primary vesico-ureteral reflux (VUR) with special attention to gender-specific differences. Between 1970 and 2004, 735 patients were diagnosed with VUR and were systematically followed in a single tertiary renal unit. The following variables were analyzed: race, age at diagnosis, clinical presentation, weight and height Z-score, unilateral/bilateral reflux, VUR grade, renal damage, severity of renal damage, constipation, and dysfunctional voiding. Comparison of proportion between genders was assessed by the chi-square test with Yates’ correction. The logistic regression model was applied to identify independent variables associated with gender. A survival analysis was performed to evaluate VUR resolution. After adjustment, five variables remained independently associated with male gender at baseline: non-white race [Odds ratio (OR) = 1.98, 95% confidence interval (95% CI) 1.33–2.95, P=0.001], moderate/severe grade of reflux (OR=2.16, 95% CI 1.45–3.22, P<0.001), severe renal damage (OR=1.60, 95% CI 1.04–2.52, P=0.04), age at diagnosis <24 months (OR=1.79, 95% CI 1.23–2.60, P=0.002), and antenatal clinical presentation (OR=3.56, 95% CI 1.91–6.63, P<0.001). Follow-up data were available for 684 patients (93%). Median follow-up time was 69 months (range 6 months to 411 months). Girls had a greater risk of urinary tract infection (UTI) during follow-up than boys (OR=1.68, 95% CI 1.18–2.38, P=0.003). There was no difference in progression to chronic renal insufficiency (CRI) between boys (3.8%) and girls (2.4%) during this period of follow-up (OR=1.58, 95% CI 0.59–4.15, P=0.44). Gender as an isolated variable is a poor predictor of clinical outcome in an unselected series of primary reflux. Although boys had a more severe pattern at baseline, girls had a greater risk of dysfunctional voiding and recurrent UTI during follow-up.